Marble busts of Emperor Hadrian and of his beloved, Antinous, represented as a young god crowned in ivy. Photograph: British Museum

There is a sculpture of the beautiful face of Antinous, at whose death Emperor Hadrian "wept like a woman"; a battered copper coin showing the poet Sappho, whose surviving fragments of erotic poetry were so intense that the Victorians called all women who loved women after her native Lesbos; and a 20-year-old tin badge demanding, "how dare you presume I'm heterosexual".

The objects are among those detailed in a new guide to be launched this month by the British Museum, tracing a history often hidden within one of the world's great collections.

A Little Gay History by Richard Parkinson, a curator in the ancient Egypt department, together with an audio guide featuring the voices of actor Simon Russell Beale and artist Maggi Hambling, will form part of the Pride festival – which will also include a special showing of the Merchant Ivory film of EM Forster's Maurice, in which the hero finds love in the galleries of the British Museum. Forster wrote the book in the early 20th century but would not allow it to be published until after his death in 1970.

After Antinous drowned in the Nile in AD130, possibly killing himself, Hadrian proclaimed him a god and displayed his image across the empire. His subsequent deep depression may have contributed to his own early death just eight years later. At the museum's blockbuster exhibition on Hadrian in 2008, a survey showed most visitors had no idea of the married emperor's intense feelings for another man.

Parkinson claims that the oldest chat-up line in history can be found in his department: a poem from 1800BC in which one ancient Egyptian male god makes a pass at another, remarking "neferwi-pehwi-ki" – what a lovely backside you have. However he concedes that many of the tender Egyptian images of two men caressing actually depict brothers, and that the graphic images on one papyrus from 950BC, including a god folded up painfully so that he can reach his penis with his mouth, are religious, not erotic, texts.

A Japanese woodblock of two men making love – one dressed as a woman, his costume as a theatre actor. Photograph: British Museum

"Desire leaves no archaeological traces," he writes, making it easy to ignore, miss or misunderstand gay references. "History has all too often been a list of the deeds of famous men who are implicitly 'heterosexual' and usually European … Unsurprisingly, lesbian, gay, bisexual and transgender people have often felt excluded and silenced, and without a voice."

The objects Parkinson has chosen, most from the British Museum but some from the British Library, include a drawing by Michelangelo showing the beautiful body of Phaeton falling from his father's sun chariot, which the artist sent to his handsome young friend Tommaso de'Cavalieri. If he didn't like it, Michelangelo promised to make another "by tomorrow evening". Parkinson writes: "The combination of the superb drawing and the elegantly written note to his friend, protesting that it is only a first sketch, embodies an infatuated eagerness to impress a young man in a way that feels instantly recognisable to anyone who has ever been in a similar situation."

He has also included some recent acquisitions, including a 1997 pack of playing cards portraying Japanese drag queens, made by the artist Takashi Otsuka, donated to the museum on condition that it is stored "with the queens on top".

A colourful quilt bought in Pakistan in 1985 is said to have been made by, or for, a hijira, a transvestite, but the curators are not sure if this is actually true. Without the story, the quilt is just a piece of cloth, Parkinson says. "Even with the anecdote, the history of its maker's life remains a blank. For all the lesbian, gay, bisexual and transgender people we can name in history, we must consider how many thousands of others are unrecorded, unacknowledged and unremembered."

In the audio trail, Hambling is particularly struck that Sappho's Greek island home valued the poet enough to put her on its official coinage. "So two Sapphos might be worth a bag of peas?" she ponders. However, looking at some of the museum's huge collection of donated protest badges, she remarks that she personally can't stand being called lesbian, just about accepts lesbionic, but prefers to refer to herself as a dyke.

Russell Beale is awed by the beauty of the Roman silver Warren Cup showing men and youths making love, so startlingly erotic that the first time the British Museum was offered it in the 1950s, it turned it down flat. In 1999, when it came on the market again, the museum had to raise £1.8m to acquire it. "It's just heaven, isn't it?" Russell Beale sighs.

From the British Museum collection

• Marble busts of Emperor Hadrian and his beloved Antinous, represented as a young god crowned in ivy.

• Treasure chest from New Zealand, made in the 18th century to be suspended so that the intricate carvings, including a stylised scene of oral sex, could be admired from all sides. Polynesian gay sex startled Captain Cook and other early explorers: a surgeon on the Discovery noted in 1779 that the locals often asked if handsome young sailors were the lovers of the officers.

• The Warren cup, a Roman wine cup decorated with scenes of men making love, said to have been found near Jerusalem, owned in the early 20th century by the American art collector Edward Perry Warren, who kept it at his home in Lewes, Sussex, and called it the "holy grail". Bought for £1.8m by the British Museum in 1999, its most expensive single purchase.

• Japanese woodblock print of two men making love – one dressed as a woman, his costume as an actor in the kabuki theatre. They are watched by a tiny figure of a man who has been shrunk by a magic spell but profits by it as a voyeur.

• Pottery lamp from 1st-century Turkey, showing two women having oral sex – though Richard Parkinson, author of A Little Gay History, says it is impossible to tell whether the lamp was made to delight women or titillate men.

• Collection of donated gay rights badges, including one by the cartoonist Kate Charlesworth insisting, "no, it simply isn't true that being a lesbian means you have to keep a cat".